A preferred method of treatment of Parkinson's disease is the administration of a combination of levodopa and a peripherally selective aromatic amino acid decarboxylase inhibitor (AADCI) together with a catechol-O-methyltransferase (COMT) inhibitor. The currently employed COMT inhibitors are tolcapone and entacapone. However, some authorities believe that each of these COMT inhibitors have residual problems relating to pharmacokinetic or pharmacodynamic properties, or to clinical efficiency or safety. Hence, not all patients get most benefit from their levodopa/AADCI/COMT inhibitor therapy.
Favoured new COMT inhibitors were disclosed in L. E. Kiss et al, J. Med. Chem., 2010, 53, 3396-3411 (D1), WO 2007/013830 (D2) and WO 2007/117165 (D3) which are believed to have particularly desirable properties so that patients can benefit from enhanced therapy.
D1, D2 and D3 also disclosed methods of preparing the new COMT inhibitors. Those processes, although effective, would benefit from an increase in yields. Other benefits which would be appropriate include those selected from reduction in number of process steps, reduction in number of unit operations, reduction of cycle-times, increased space yield, increased safety, easier to handle reagents/reactants and/or increase in purity of the COMT inhibitor, especially when manufacture of larger quantities are envisaged. A process has now been discovered that proceeds via a new intermediate which is suitable for manufacture of commercially useful quantities of a particularly apt COMT inhibitor in good yield. Additional benefits occur such as those selected from a reduced number of process steps and number of unit operations, reduced cycle-times, increased space yield, increased safety, with easier to handle reagents/reactants, improved impurity profile and/or good purity.